The present invention generally relates to thin films, and in some embodiments, thin films for a system for neural applications, methods of manufacturing of thin films, wafers, lead cores for a lead, leads, probes and systems for neural applications. Implantable neurostimulation devices have been used for the past ten and more years to treat acute or chronic neurological conditions. Deep brain stimulation (DBS), the mild electrical stimulation of sub-cortical structures, belongs to this category of implantable devices, and has been shown to be therapeutically effective for Parkinson's disease, Dystonia, and Tremor. New applications of DBS in the domain of psychiatric disorders like obsessive compulsive disorder or depression are being researched and show promising results. In existing systems, probes carrying electrodes are connected to an implantable pulse generator (IPG).
Future systems will need more, smaller electrodes, in order to better control the delivery of electrical stimulation, because current stimulation causes mild to severe side-effects in about 30% of the patients. Magnetic resonance (MR) safety of these implantable devices is an important issue. MR safety, reduction of the heating of the implant as a result of the electrical field during MR scanning, can be realized by winding of the cable wires on the device. However, the winding substantially increases the length of the cable wiring. The DBS lead can be manufactured by winding a thin film around a core. These thin films are typically produced on a carrier wafer or a plate and released from the wafer or plate after manufacturing. In the case of a DBS lead that is manufactured with winded thin film, the length of the thin film is substantial and can exceed the size of the carrier substrate.
Thin films for implanted DBS systems are typically manufactured on a carrier wafer. In general, silicon carrier substrates of either 6 inch (15.24 cm) or 8 inch (20.32 cm) diameter are used. However, a MR safe DBS system will need a thin film of several tens of centimeters. This length exceeds the diameter of the carrier wafer and a simple straight thin film cannot be made.
A known method to overcome this limitation of the carrier substrate size makes use of a foldable thin film design as described in U.S. Patent Application Publication No. 2007/0123765 A1, which is hereby incorporated by reference in its entirety. The folding method has several disadvantages though. Folding the film severely compromises the mechanical properties of the thin film. Folding forces the thin film into a small radius of curvature and stretches the materials at the outer side of the curvature. Meanwhile the folding strains the materials at the inside of the curvature and can cause the materials in the thin film to crack, break and buckle. Moreover, the manufacturing process of leads, the winding of the thin film around a core, is more complicated. At the position of folding, the winding process must be discontinued. The discontinuity of the thin film folding disrupts the winding process of the film around a core.
It is therefore desirable to improve a thin film, a method of manufacturing of a thin film, a wafer, a lead core for a lead, a lead, a probe and a system for neural applications, especially in that thin films can be provided without folding and which exceed the dimensions of a substrate on which the thin film is manufactured.